We have synthesized the activated form of the carcinogen benzo(a)pyrene, which is plus or minus 7alpha,8beta-dihydroxy-9alpha,10alpha-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene (I), and determined through fluorescence, absorbance and circular dichroism spectroscopy and high resolution mass spectroscopy that the hydrocarbon reacts to form six adducts with DNA. Two adducts each are formed with deoxyguanosine, deoxyadenosine and deoxycytidine and the relative levels with each base were 92, 5 and 3%, respectively. The hydrocarbon was shown to be bound through its C10-position to the exocyclic amino groups of guanine and adenine and probably cytosine as well. Resolution of plus or minus I and reaction of the optically pure enantiomers with DNA demonstrate that the pair of adducts with each base were diastereomers. The ratio of disastereomers derived from the plus and minus enantiomers of (I) were 20:1 for guanine, 5-10:1 cytosine and 1:1 adenine. This proposal is designed to investigate 1) the nature of the stereoselectivity in the non-enzymatic reactions of plus I and DNA, 2) the role of intercalation, 3) mutagenesis mechanisms resulting from binding, and 4) the relevance of adducts to the biological properties of the hydrocarbon. Our hypothesis that stereoselective binding is a result of DNA secondary structure will be tested by reaction of I with a denatured polymer. Based on preliminary evidence that I intercalates prior to alkylation, sequence specific interactions will be investigated by DNA sequencing techniques and nearest neighbor analysis. Mutagenesis mechanisms will be studied by reaction of plus or minus I with a restriction fragment, followed by replication of the modified fragment and sequencing of the newly synthesized strand. In vivo adducts formed within target (skin and lung) and non-target (liver and kidney) tissues will be analyzed by comparison to known in vitro products, to determine their relevance to the biological properties of benzo(a)pyrene.